The invention set forth in this specification pertains to new and improved seal structures intended to be utilized within dispensing closures employing polyolefin parts and constructed in such a manner that when the parts are assembled with respect to one another one of the parts may be rotated relative to the other of the parts between open and closed positions. It is considered, however, that these seal structures may be utilized with other related devices.
Dispensing closures as indicated in the preceding discussion are normally constructed using two parts, one of which is a rotatable part serving as a bottle cap and the other of which is a rotatable part serving as a spout which can be manipulated without removing the bottle cap from a container. Such closures may be constructed using more than two parts; they are widely utilized in packaging many different types of liquid or semi-liquid type products. These closures have been widely utilized because they can be easily and conveniently manufactured at a comparatively nominal cost. In spite of this the utilization of dispensing closures has been somewhat limited by the problem of forming closures which would not leak when used with the various different materials.
This problem of leakage in dispensing closures constructed utilizing polyolefin parts has been much more severe than anyone who has not been directly involved in the dispensing closure field would ever imagine. Virtually since the inception of such closures leakage has continually been a problem. During the early days of these dispensing closures it was thought that leakage could be prevented by utilizing congruent parts in the areas of such closures adjacent to openings and the passages through the parts of such closures. This was found not to be the case, primarily as a result of what was once termed the "idiosyncrasies" of the polyolefin then used for manufacturing these closures--polyethylene. Because of shrinkage and other factors it was found virtually impossible to manufacture polyethylene to exacting tolerances necessary to form effective seals against many different comparatively hard to seal liquids.
Efforts at creating effective seals for dispensing closures as noted have led to the development of a number of different structures. Virtually all of such structures have involved shaping the bottom of the non-movable part within such closure in one manner or another so that the contact between the two parts would result in either an increased pressure between the parts or a temporary deformation serving to prevent leakage. It is considered that an understanding of this invention requires a detailed discussion of the partial O-ring, more or less blade shaped pressure pad and various other related sealing members or structures which have been utilized with dispensing closures as indicated in the preceding discussion.
As the field of such closures is developed more and more effective seals have been developed. As comparatively hard, but still somewhat deformable, somewhat resilient materials such as polypropylene and linear polyethylene have become available, these materials have been increasingly used in two-part dispensing closures as noted for a number of reasons. One very important one of these reasons relates to that fact that many purchasers of dispensing closures prefer closures made of these materials because of their surface appearances and characteristics.
Efforts to shift to the use of polypropylene and linear polyethylene in manufacturing dispensing closures as noted have been handicapped to a degree by the fact that these materials are not as resilient and flexible as the non-linear polyethylene previously employed in manufacturing the parts of these closures. As the result of the comparative rigidity with these materials, the seal structures previously employed have not always proved satisfactory. The degree of effectiveness of such seal structures is, of course, related to a multitude of factors in connection with the design of any specific dispensing closure.
One of these factors pertains to the relative sizes of the parts. There is increasingly a tendency to produce dispensing closures having comparatively large openings or passages in the parts employed. Generally speaking, the larger such parts are or the larger such openings are, the more difficulty there is in providing a seal member or structure which will effectively seal against leakage of various comparatively hard to seal liquids and semiliquids. It is to be recognized that this problem of leakage is quite involved because it involves not only surface irregularities and deformations, but it involves fluid tension considerations related to both the liquid or the like being sealed and the material or materials which contact one another so as to form a seal.